In normal straight ahead walking and running, the average person contacts the heel first in the stance phase of gait. At the time of ground contact, the heel hits on the outside or lateral side, gradually shifts to the inner portion of the heel and then to the outer side of the foot over the metatarsals and then finally through the great toe for the final phase of propulsion. The period of time from the initial heel contact to the stage when the foot is flat is about the first 20 to 25% of the gait. At the time of heel contact when the body weight is borne on the heel, the leg is internally rotating, the ankle joint is dorsiflexing, and the sub-talar joints are pronating to accommodate any uneven surface and to cushion the shock of the body weight as it passes from the center of gravity through the ankle, the sub-talar joints and the foot.
The estimated body weight during walking is about 11/2 to 2 times the normal body weight at the heel strike and 2 to 4 times the normal body weight during running.
It is the purpose of this invention to provide a device which will so modify the biomechanics of walking, jogging and running to mitigate impact at heel contact to the foot flat state and to develop an external rotational force on the heel and tibiofibular unit of the leg to cause supination. The device of this invention decreases the end range of pronation of the sub-talar joints preventing overuse syndrome characterized by Achilles Tendonitis, posterior tibial tendonitis, shin splints, runner's knee, and various other maladies affecting the foot, ankle and leg.